Bearings for an open-end spinning turbine

ABSTRACT

Bearing means for the turbine shaft of an open-end spinning turbine in which this shaft extends, for example, substantially horizontally, comprising supporting rollers mounted underneath and at both sides of the turbine shaft and forming at least one wedge-shaped gap between them in which the turbine shaft is supported on the rollers and is pressed thereon and directly driven, for example, by a drive belt. For producing an axial thrust of the turbine shaft toward and against a thrust bearing, the shafts of the supporting rollers at both sides of the turbine shaft extend parallel to the turbine shaft as seen in a top view, but as seen in a side view they are inclined about an axis extending transverse to and underneath the turbine shaft.

llnited States Patent Stahleclter Dec. 18, 1973 [54] BEARENGS FOR AN OPEN-END SPINNING 2,582,563 1/1952 Romero 308/162 TURBINE 2,828.938 4/1958 Roesch et al. 308/203 Inventor: Fritz Stahleclker, Bad Uberkingen,

Germany Assignee: Wilhelm GmbH, Reichenbach,

Germany Filed: Mar. 16, 1972 Appl. N0.: 235,319

Foreign Application Priority Data 7 Mar. 17, 1971 Germany P 21 12 913.5

References Cited UNlTED STATES PATENTS 11/1910 Helbig 12/1969 Franzen 11/1952 Gehre 308/203 Primary Examiner-Charles J. Myhre Assistant ExaminerBarry Grossman Attorney-Paul M. Craig, Jr. et al.

[5 7] ABSTRACT Bearing means for the turbine shaft of an open-end spinning turbine in which this shaft extends, for example, substantially horizontally, comprising supporting rollers mounted underneath and at both sides of the turbine shaft and forming at least one wedge-shaped gap between them in which the turbine shaft is supported on the rollers and is pressed thereon and directly driven, for example, by a drive belt. For producing an axial thrust of the turbine shaft toward and against a thrust bearing, the shafts of the supporting rollers at both sides of the turbine shaft extend parallel to the turbine shaft as seen in a top view, but as seen in a side view they are inclined about an axis extending transverse to and underneath the turbine shaft.

12 Claims, 6 Drawing Figures PATENIEUUEC18 191s 3.7T9L620 SHEET HP 3 BEARINGS FOR AN OPEN-END SPINNING I TURBINE The present invention relates to a bearing unit for an open-end spinning turbine which is of the type in which the shaft of the turbine is radially supported within one or more wedge-shaped gaps which are formed between rotatable supporting or bearing rollers which are preferably provided with covers of plastic, and which is supported in one axial direction by a thrust bearing.

When supported by bearings of this type, the shaft of the turbine may be driven directly by a driving element acting thereon, especially by a belt such as a tangential belt. It is, however, also possible to drive the turbine shaft by means of the supporting rollers in which case an additional pressure roller must be provided for maintaining the turbine shaft within the wedge-shaped gap between the supporting rollers and in engagement with the latter which in the first-mentioned case is done by the driving element which acts directly upon the turbine shaft.

Since a spinning turbine should not be movable in its axial direction relative to the yarn supply means, suitable provisions must be made to exert an axial force upon the turbine shaft which insures that the end of this shaft opposite to the end carrying the turbine will be pressed at all times firmly against a thrust bearing. For this purpose it is already known to employ a driving element which has a slightly inclined surface engaging with the turbine shaft. If the turbine shafts of several spinning units are driven by a common drive belt, all of these shafts are mounted so as to extend at a suitable angle differing from a right angle to the direction of travel of the drive belt. This requires a considerable expense for properly mounting the turbine shafts and for driving the latter, the drive belt is also subjected to additional stresses. The axial force which is produced by inclining the turbine shaft at such an angle to the direction of travel of the drive belt acts as a reactive force of the same value upon the belt which then has to be supported at one lateral side between the individual spinning units. This is generally done by means of additional rollers which are provided with lateral guide flanges. Such guide flanges exert, however, a considerable wear upon the adjacent lateral edge of the drive belt, a wear which may be often so strong that it will considerably reduce the normal length of service of the belt or cause its early destruction. These difficulties occur especially if for producing yarns of a particular quality the spinning turbines have to be driven at a very high speed by the drive belt which also maintains the turbines in their proper axial positions.

Prior to this invention it has also been proposed to produce the required axial thrust of the turbine shaft by mounting the turbine and its shaft so as to extend substantially vertically sothat the axial thrust will be produced by their own weight. Such spinning turbines can, however, only be very rarelyemployed because they have various disadvantages, especially insofar as the spinning operation is concerned.

In order to overcome these disadvantages, it is also known to produce the required axial thrust of the turbine shaft in the direction toward the thrust bearing by employing permanent magnets or by mounting propellers or the like on the spinning turbine or on its shaft. Although such means prevent the driving element from being excessively worn, they consume additional energy and therefore require an increased driving force.

Furthermore, if permanent magnets are employed which are relatively costly, it is particularly unavoidable that in the course of time their efficiency will decrease.

It is an object of the invention to provide a bearing unit of the type as first mentioned above which, apart from radially supporting the shaft of an open-end spinning turbine, is also adapted to produce an axial thrust of this shaft of a sufficient strength which may be accurately predetermined, and which despite this requirement may be produced at a very low cost.

For attaining this object, the invention provides that the shaft of at least one of two associated supporting rollers between which the wedge-shaped gap is formed in which the turbine shaft is rotatably suported extends at a small inclination to the turbine shaft, as seen in a direction transverse to the central axial plane of the wedge-shaped gap between the two associated supporting rollers and radially to the turbine shaft. The axial thrust of the turbine shaft which is thus produced depends primarily upon the particular angle of the inclination of the shaft or shafts of the supporting roller or rollers and upon the coefficient of friction between the turbine shaft and the supporting rollers. This angle must therefore be accurately predetermined or accurately adjustable.

According to another embodiment of the invention, the shafts of all of the supporting rollers are inclined relative to the turbine shaft in the direction as stated above, but the shaft or shafts of the supporting roller or rollers at each side of the turbine shaft are inclined in a direction opposite to the direction of the shaft or shafts at the other side of the turbine shaft. Due to these opposite inclinations of the shafts of the supporting rollers, the effects of the latter upon the turbine shaft do not counteract but supplement each other. This permits the angles of inclination of these shafts relative to the turbine shaft to be made so small that, if several supporting rollers are provided at each side of and underneath the turbine shaft, these rollers may be mounted on a common shaft. Therefore, both shafts of the two sets of supporting rollers are then inclined in opposite directions to each other and preferably about a common axis which extends transverse to and underneath the turbine shaft.

According to another preferred embodiment of the invention, at least the shaft of the supporting roller or rollers at one side of the turbine shaft is rotatably mounted in a bearing bracket which is pivotably adjustable about an axis which extends transverse to the turbine shaft. This bearing bracket is preferably provided with a pointer which is associated with a stationary scale and permits the axial thrust of the turbine shaft to be accurately adjusted to the desired strength and to be indicated.

An additional feature of the invention consists in increasing the axial thrust of the turbine shaft by slightly inclining the driving or guide element which acts directly upon the turbine shaft in the direction toward the thrust bearing of this shaft. However, since this driving or guide element is only intended to produce a small component of the axial thrust, the stresses, if any, to which it will then be subjected will only slightly exceed the stresses to which it is normally subjected by its driving or guiding action. The principal purpose of this feature is to compensate any inaccuracy of the desired axial thrust of the turbine shaft as produced by the supporting rollers which may be due to small tolerances in the manufacture of these rollers.

It is another object of the invention to provide a suitable brake for stopping the turbine shaft and for insuring that the required axial thrust of this shaft toward its thrust bearing will be maintained when the driving element of this shaft is being lifted ofi the latter. For at taining this object, the invention provides that the brake linings of this brake and/or the turbine shaft are made of such a shape that when these brake linings are pressed upon the turbine shaft a force component of this pressure will also be exerted upon this shaft which tends to shift the latter in the direction toward the thrust bearing. According to one preferred embodiment of the invention, this may be attained by providing each of the parts of the turbine shaft upon which the brake linings are applied with a helically shaped groove, which according to another embodiment of the invention at least one ring is secured upon the turbine shaft and one side of this ring opposite to the side facing the thrust bearing is made of a conical shape. When the brake is being applied, the edge of one of the brake linings facing the thrust bearing slides along this conical side of the ring and thereby exerts an axial thrust upon the turbine shaft in the direction toward the thrust bearing.

The-features and advantages of the present invention will become further apparent from the following detaileddescription thereof which is to be read with reference to the accompanying drawings, in which:

FIG. 1 shows a side view of a bearing unit according to the invention;

FIG. 2 shows a top view of the bearing unit according to FIG. 1;

FIG. 3 shows a side view of a bearing unit according to another embodiment of the invention;

FIG. 4 shows a side view, partly in section, of a bearing unit according to another embodiment of the invention;

FIG. 5 shows a side view, partly in section, of a bearing unit according to a further embodiment of the invention; while FIG. 6 shows a side view of a bearing unit according to a modification of the unit as shown in FIG. 5.

In the drawings, FIGS. 1 and 2 only show parts of an open-end spinning unit, namely, the spinning turbine 1, its shaft 2, two pairs of supporting or bearing rollers 3, 4, 5 and 6 for the shaft 2, a drive belt 7 which acts directly upon the turbine shaft 2, and a thrust bearing 8 upon which the crowned end of shaft 2 bears in the axial direction of this shaft.

The two pairs of supporting rollers 3 to 6 are mounted relative to each other so as to form wedges haped gaps between the opposite rollers 3 and 5 as well as 4 and 6 in which the turbine shaft 2 is radially supported. Aside from driving the shafts 2 of several or all spinning turbines of one side of the spinning machine, drive belt 7 which is only indicated in dotted lines in FIG. 2 also maintains each turbine shaft 2 in a radial direction within the wedge-shaped gaps between the supporting rollers 3 to 6. In addition it is necessary to exert upon the turbine shaft 2 an axial force so as to produce an axial thrust of this shaft upon the thrust bearing 8. According to the embodiment of the invention as illustrated in FIGS. 1 and 2, this thrust bearing 8 comprises a bearing plate 9 upon which the crowned end of shaft 2 engages. Above bearing plate 9, a feed pipe 10 terminates through which a lubricant, for example, oil may be constantly supplied to the crowned end of shaft 2, preferably from a common supply for all of the spinning units of the machine. Underneath the bearing plate 9 an oil collecting trough 11 is provided which extends in the longitudinal direction of the machine transversely to several adjacent spinning units.

The required axial thrust of the turbine shaft 2 in the direction toward the thrust bearing 8 may be attained in this embodiment of the invention by the particular construction and arrangement of the radial bearings of the shaft. Therefore aside from the pressure which the drive belt has to exert upon the turbine shaft 2, so as to drive the same and to press it upon the supporting rollers 3 to 6, this belt will not be subjected to additional stresses for producing an axial thrust of shaft 2. The two pairs of supporting rollers 3, 4 and 5, 6 are mounted at the opposite sides of and underneath the turbine shaft 2 on common shafts l2 and 13, respectively, the bearings of which are located between the rollers of each pair. While extending in one direction within planes which are parallel to the axis of turbine shaft-2 and parallel to the direction of the central vertical plane of the wedge-shaped gaps between the two pairs of rollers 3 to 6, these shafts l2 and 13 are slightly inclined relative to the turbine shaft 2 as seen in a direction transverse to this central plane of the wedgeshaped gaps and radially to the turbine shaft 2, but they are inclined in opposite directions relative to each other and relative to shaft 2 at an angle a about an axis 14 which extends transverse to and underneath the turbine shaft 2 and substantially centrally between each pair of supporting rollers 3, 4 and 5, 6, respectively. This angle a between shafts 12 and 13 is made of such a size that all supporting rollers 3 to 6 will exert a force upon the turbine shaft 2 which tends to shift the latter in its axial direction toward the thrust bearing 8. The inclination of shafts 12 and 13 in one direction or the other depends upon the direction of travel of the drive belt 7 which in FIG. 2 is assumed to extend in the direction of the arrow 15. Thus, shaft 12 which, as seen in this direction 15, is located in front of the turbine shaft 2 is turned in the clockwise direction about the axis 14, while the other shaft 13 which is located behind the turbine shaft 2 is turned in the counterclockwise direction about tha axis 14. The angles at which both shafts l2 and 13 are inclined in opposite directions relative to a plane extending parallel to the longitudinal axis of the turbine shaft 2 together amount of the angle a which for the purpose of a better illustration is shown in FIG. 2 considerably larger than it would be in actual practice in which it would only amount to approximately l. Since this angle is so small, it is easily possible to mount each pair of supporting rollers 3 and 4 or 5 and 6 on a common shaft 12 or 13, respectively. This is true especially since preferably each of the supporting rollers is covered with a tread layer of a resilient plastic, which engages within the wedge-shaped gaps with the turbine shaft 2.

The strength of the axial thrust of the turbine shaft 2 toward the thrust bearing 8 depends upon the angle a, the coefficient of friction between the tread layers of plastic on the rollers 3 to 6 and shaft 2, the pressure which the drive belt 7 exerts upon shaft 2 and the speed at which the latter is driven. Since all of these values may be very accurately determined, the axial thrust of shaft 2 may also be very accurately adjusted to a value which remains practically constant at all times.

For proper operation of the bearing unit as described it is advisable to insure that the drive belt 7 will have such a direction of travel relative to the direction of the turbine shaft 2 that it will under no circumstances produce an axial thrust of shaft 2 which is opposed to the axial thrust which is produced by the supporting rollers. Therefore, the angle B between the turbine shaft 2 and the traveling drive belt 7 behind its engagement with shaft 2 and at the side of the belt facing the thrust bearing 8 should have a value not exceeding 90". If this angle ,8 is made smaller than 90, the drive belt'7 will produce an additional axial thrust of the turbine shaft 2 in the direction toward the thrust bearing 8 which increases the thrust which is produced by the supporting rollers 3 to 6.

In some cases it may be advisable to increase the axial thrust of the turbine shaft by additional conventional means or procedures, especially if in the housing containing the spinning turbine 1 a relatively high vacuum should be produced which counteracts the axial thrust of the turbine shaft 2. Since these means or procedures such as an inclining of the direction of travel of the drive belt to an angle differing from a right angle relative to the turbine shaft as last described or the use of a magnet or of a propel'lerlike means are to be merely supplementary to the application of the invention, the effect which they should produce also only needs to be supplementary and may therefore be considerably lower than that which would be required if they were applied alone. Consequently, the disadvantages which these means or procedures would possess in the latter case will also be reduced considerably. The axial thrust of the turbine shaft in the direction toward the thrust bearing 8 may also be increased, for example, by providing the turbine shaft 2 or the tread surfaces of the supporting rollers engaging with this shaft with screw threads.

FIG. 3 which shows an embodiment of the invention which in principle corresponds to the embodiment as shown in FIGS. 1 and 2 illustrates an apparatus of a very simple construction for adjusting the roller shafts 12 and 13 to the desired inclinations relative to the turbine shaft 2. The bearing of at last one of the shafts 12 or 13 is secured to an annular bearing bracket 16 which is pivotably mounted on a stationary part 17 of the machine and adapted to be locked to the latter in the particular position to which it is pivoted by means of a screw 20 which extends through an elongated hole 19 in an arm on the bearing bracket 16 and is screwed into the machine part 17. An extension of this arm of the bearing bracket 16 which projects beyond the elongated hole 19 is provided with a raised or depressed part forming a pointer 21 which indicates on a fixed scale 22 the particular angle a to which the bearing bracket carrying the shaft 12 or 13 is pivoted. This scale 22 may, however, also form a separate element which is adjustably mounted on the machine part 17 so as to permit a basic adjustment of this scale 22 by the manufacturer of the machine in accordance with the measurements of the axial thrust of the turbine shaft 2 which may be made by a special instrument on the thrust bearing 8. If subsequently in the spinning factory the roller shafts 12 and 13 of all spinning units of a spinning machine are adjusted so as to have the same angle a relative to the turbine shafts 2, the axial thrust of all turbine shafts will also have the same strength.

Frequently it will be sufficient to provide only one of the two pairs of supporting rollers 3, 4 or 5, 6 with an adjustable bearing bracket 16 since a small adjustment of the angle of the bearing bracket 16 and thus also of the shaft 12 or 13 necessarily causes a small inclination of the turbine shaft 2 from its normal position so that the two shafts 12 and 13 will also be inclined relative to each other.

FIG. 4 illustrates an embodiment of the invention in which the wedge-shaped gap for receiving the turbine shaft 2 is formed between two longer supporting rollers 23 and 24 which are rotatably mounted at both sides of and underneath the turbine shaft 2. The shafts 12 and 13 of these supporting rollers 23 and 24 which are likewise covered with layers of a resilient plastic are inclined relative to each other in the same manner as previously described so that an axial thrust will be exerted upon the turbine shaft 2 in the direction toward the thrust bearing 8. The turbine shaft 2 is in this case driven indirectly by means of the supporting rollers 23 and 24 the shafts l2 and 13 of which are for this purpose provided with rollerlike drive pulleys 25 along which a drive belt 26 is adapted to run. Whether each of the shafts 12 and 13 is inclined in one or the other direction relative to the turbine shaft 2 depends also in this case upon the direction of rotation of the spinning turbine 1 an its shaft 2. The angles at which these shafts 12 and 13 are actually inclined are again considerably smaller than those as illustrated. The supporting rollers 23 and 24 are again provided with covers of a resilient plastic which insure that the contact between the turbine shaft 2 and the two supporting rollers 23 and 24 will not be merely pointlike but along the entire length of these rollers.

For maintaining the turbine shaft 2 within the wedgeshaped gap between the supporting rollers 23 and 24, the apparatus according to FIG. 4 is provided with a pressure roller 27 which presses the turbine shaft from above into the wedge-shaped gap. This pressure roller 27 is rotatably mounted on one end of an arm 28 the other end of which is pivotably mounted on a turbine housing 29 and is acted upon by a spring 41, which presses the roller 27 with the required force upon the turbine shaft 2.

For stopping the spinning turbine 1 of either of the spinning units as shown in FIGS. 1 to 3 while the drive belt 7 continues to run, the latter should be lifted off the turbine shaft 2 and at the same time a brake should be applied upon this shaft. Suitable provisions should then be made to insure that during the period in which the drive belt 7 is being lifted and the brake is being applied, the required axial thrust of the turbine shaft 2 will be maintained and the position of the latter will not be effected. Two embodiments of the turbine and bearing units which are designed to accomplish this purpose are illustrated diagrammatically in FIGS. 5 and 6. According to FIG. 5 a thrust bearing 8 is provided which comprises a housing in which a bearing disk 31 on which the crowned end of the turbine shaft 2 is supported is adapted to revolve about a shaft 30. This bearing disk 31 is maintained in a fixed position in the axial direction of the turbine shaft 2 by means of an adjustable setscrew 32.The lower part of this housing forms an oil bath in which the bearing disk 31 is rotatable. The cover 33 of the housing carries several sealing disks 34 which are provided with bores through which the turbine shaft 2 extends. These sealing disks 34 prevent the oil from passing out of the housing and they also serve as a support for carrying the shaft 30 so that, when the cover 33 is removed from the housing after the turbine shaft 2 has been withdrawn, shaft 30 and the bearing disk 31 thereon will likewise be removed from the housing.

The brake which may be applied upon the turbine shaft 2 for stopping the spinning turbine 1 may be of a conventional construction of which in FIG. 5 only the brake linings 36 are illustrated which are secured to one or a pair of leaf springs 35. According to the invention, the two parts of the turbine shaft 2 upon which these brake linings 36 may be applied are provided with grooves 37 which are cut in the form of helical threads and produce a screwlike effect and thereby an axial thrust of the turbine shaft 2 in the direction toward the thrust bearing 8 when the brake linings 36 are pressed against the turbine shaft. The outer edges of these screw threads are preferably chamfered.

FIG. 6 illustrates another embodiment of the invention which is provided with a brake which aside from its braking action is adapted to maintain the turbine shaft 2 in its proper position and to produce the required axial thrust of this shaft against its thrust bearing 8 during the interval in which the drive belt 7 is being lifted off this shaft and until the latter has been stopped completely. This brake as such may likewise be of a conventional construction and therefore only its brake linings 36 and a leaf spring 35 on which they are mounted are illustrated in FIG. 6. The abovementioned purpose of this brake is attained by securing a ring 39 on the turbine shaft 2 which is provided on is front side facing the turbine l with a conical surface. When the brake linings 36 are moved toward the turbine shaft 2, an edge of one of these linings engages upon and presses against the conical surface of ring 39 and thereby exerts an axial thrust upon the turbine shaft in the direction toward the thrust bearing 8. This ring 39 has an outer diameter which is substantially equal to that of the hub or flange 38 on the turbine 1 so that, after the turbine shaft 2 has been stopped and the brake linings 36 have been withdrawn from the latter, the turbine 1 together with its shaft 2 may be easily pulled forwardly out of the turbine housing without danger that the plastic covers on the supporting rollers 3 to 6 might thereby be damaged.

In all of the embodiments of the invention as illustrated and described it is assumed that in its actual operation the spinning turbine is driven only in one direction. This is a condition which for practical reasons is inveriably followed in open-end spinning turbines. The desired value of the axial thrust of the turbine shaft depends upon the size of the spinning turbine and the strength of the vacuum in the housing surrounding the turbine and lies between 300 and 800 p. The angle of inclination a of the shafts of the supporting rollers may, however, also be made of such a size that the axial thrust of the turbine shaft will exceed these values.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, 1 wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what i claim is:

l. A bearing unit for an open-end spinning turbine having a turbine shaft, a spinning turbine secured to one end of said shaft, a thrust bearing upon which the other end of said shaft is adapted to engage, at least one pair of supporting rollers having shafts, mounting means for mounting said roller shafts underneath and at opposite sides of said turbine shaft so that a wedgeshaped gap is formed between the peripheral surfaces of said rollers in which said turbine shaft is located and rotatable on said rollers, driving and guide means normally acting directly upon said turbine shaft for driving the same and for maintaining it in contact with said rollers, said shaft of at least one of said rollers extending at an inclination relative to said turbine shaft as seen in a direction transverse to the central longitudinal plane of said wedge-shaped gap and radially to said turbine shaft, whereby when said turbine shaft is driven, said roller shaft exerts an axial thrust upon said turbine shaft which maintains said other end of said turbine shaft in constant engagement with said thrust bearing.

2. A bearing unit as defined in claim I, in which said roller shaft at both sides of said turbine shaft extend at similar inclinations relative to said turbine shaft but are inclined in opposite directions to each other.

3. A bearing unit as defined in claim 2, in which at least two of said supporting rollers are mounted at each side of said turbine shaft on a common roller shaft, said roller shafts on both sides of said turbine shaft having similar inclinations but are inclined in opposite directions relative to each other and to said turbine shaft.

4. A bearing unit as defined in claim 3, in which said roller shafts at both sides of said turbine shaft are inclined about a common axis extending underneath and transverse to the said turbine shaft.

5. A bearing unit as defined in claim 2, in which said mounting means for said roller shaft at least at one side of and underneath said turbine shaft comprise a bearing bracket, and means for mounting said bracket so as to be pivotably adjustable about an axis extending underneath and transverse to said turbine shaft, and means for locking said bracket in the position to which it has been adjusted.

6. A bearing unit as defined in claim 5, further comprising indicating means for indicating the particular angle to which said bracket and said roller shaft mounted thereon are adjusted.

7. A bearing unit as defined in claim 1, in which one of said driving and guide means is disposed and movable in a direction which deviates slightly from a right angle to the longitudinal direction of said turbine shaft so as to increase the axial thrust of said turbine shaft toward said thrust bearing.

8. A bearing unit as defined in claim 1, further comprising a brake for stopping said turbine shaft, said brake having brake surfaces adapted to be moved said turbine shaft in the longitudinal direction thereof.

10. A hearing unit as defined in claim 8, in which at least one ring is secured on said turbine shaft, said ring having a conical surface on its side facing said turbine, at least one of said brake linings having a lateral edge adapted to engage upon said conical surface and tending to shift said turbine shaft in the direction toward said thrust bearing when said brake linings are being moved toward said turbine shaft.

11. A bearing unit as defined in claim 1, in which said driving and guide means comprise a drive belt. 

1. A bearing unit for an open-end spinning turbine having a turbine shaft, a spinning turbine secured to one end of said shaft, a thrust bearing upon which the other end of said shaft is adapted to engage, at least one pair of supporting rollers having shafts, mounting means for mounting said roller shafts underneath and at opposite sides of said turbine shaft so that a wedgeshaped gap is formed between the peripheral surfaces of said rollers in which said turbine shaft is located and rotatable on said rollers, driving and guide means normally acting directly upon said turbine shaft for driving the same and for maintaining it in contact with said rollers, said shaft of at least one of said rollers extending at an inclination relative to said turbine shaft as seen in a direction transverse to the central longitudinal plane of said wedge-shaped gap and radially to said turbine shaft, whereby when said turbine shaft is driven, said roller shaft exerts an axial thrust upon said turbine shaft which maintains said other end of said turbine shaft in constant engagement with said thrust bearing.
 2. A bearing unit as defined in claim 1, in which said roller shaft at both sides of said turbine shaft extend at similar inclinations relative to said turbine shaft but are inclined in opposite directions to each other.
 3. A bearing unit as defined in claim 2, in which at least two of said supporting rollers are mounted at each side of said turbine shaft on a common roller shaft, said roller shafts on both sides of said turbine shaft having similar inclinations but are inclined in opposite directions relative to each other and to said turbine shaft.
 4. A bearing unit as defined in claim 3, in which said roller shafts at both sides of said turbine shaft are inclined about a common axis extending underneath and transverse to the said turbine shaft.
 5. A bearing unit as defined in claiM 2, in which said mounting means for said roller shaft at least at one side of and underneath said turbine shaft comprise a bearing bracket, and means for mounting said bracket so as to be pivotably adjustable about an axis extending underneath and transverse to said turbine shaft, and means for locking said bracket in the position to which it has been adjusted.
 6. A bearing unit as defined in claim 5, further comprising indicating means for indicating the particular angle to which said bracket and said roller shaft mounted thereon are adjusted.
 7. A bearing unit as defined in claim 1, in which one of said driving and guide means is disposed and movable in a direction which deviates slightly from a right angle to the longitudinal direction of said turbine shaft so as to increase the axial thrust of said turbine shaft toward said thrust bearing.
 8. A bearing unit as defined in claim 1, further comprising a brake for stopping said turbine shaft, said brake having brake surfaces adapted to be moved toward and pressed against surfaces of said turbine shaft, said surfaces of at least one of these elements having such a shape that when said brake surfaces are pressed against said shaft surfaces a force component is exerted upon said turbine shaft which tends to move said turbine shaft toward and in engagement with said thrust bearing.
 9. A bearing unit as defined in claim 8, in which said surfaces of said turbine shaft are provided with helical grooves cut into and winding around the peripherby of said turbine shaft in the longitudinal direction thereof.
 10. A bearing unit as defined in claim 8, in which at least one ring is secured on said turbine shaft, said ring having a conical surface on its side facing said turbine, at least one of said brake linings having a lateral edge adapted to engage upon said conical surface and tending to shift said turbine shaft in the direction toward said thrust bearing when said brake linings are being moved toward said turbine shaft.
 11. A bearing unit as defined in claim 1, in which said driving and guide means comprise a drive belt.
 12. A bearing unit as defined in claim 3, further comprising a drive pulley secured to each of said two roller shafts, said driving means comprising a drive belt engaging upon both of said drive pulleys for driving said roller shafts, said guide means comprising a pressure roller and spring means for pressing said pressure roller upon said turbine shaft and for thereby pressing said turbine shaft into engagement with said supporting rollers within said wedge-shaped gap. 